He has red - fox-coloured - hair, wears tweeds, and smokes a cigar. He has a very engaging smile and a friendly laugh, but also has a terrible temper when crossed.
He is an enchanter.
Miranda greatly respects her brother, and turns to him for help when her husband loses his money (which was her money) on the stock market. He arranges for Christopher to begin boarding school, and for Miss Bell to be Christopher's governess until term starts (and, subsequently, a companion for Miranda).
Following his mother's cue, Christopher thinks a great deal of his uncle as well.